Figure 4

Adsorption of methylene blue (striped bars, scale on left axis) co-visualized with the specific surface area (black line, scale on left axis) and O:C ratio (solid grey area; scale on right axis) for all generated hydrochars. Values shown are single point values except those for 5 h at 220 °C, which are means of two samples in the initially acidic case and four samples in the initially neutral case. Error bars for initially acidic conditions represent the individual samples. Error bars for initially neutral conditions represent ± 1 standard deviation for the four centre point replicates.